Drug Interactions between conivaptan and sirolimus

GENERALLY AVOID: Coadministration with potent inhibitors of CYP450 3A4 and/or P-glycoprotein (P-gp) may significantly increase the plasma concentrations of sirolimus following oral administration. Sirolimus is a substrate of both CYP450 3A4 isoenzyme and P-gp efflux transporter, thus their inhibition in the intestine can enhance the absorption of sirolimus. In 23 healthy volunteers, administration of a single 5 mg dose of sirolimus with the potent dual CYP450 3A4/P-gp inhibitor ketoconazole (200 mg/day orally for 10 days) increased mean sirolimus peak plasma concentration (Cmax) and systemic exposure (AUC) by approximately 4- and 11-fold, respectively. Likewise, posaconazole (400 mg oral suspension twice a day for 16 days) increased mean Cmax and AUC of a single 2 mg dose of sirolimus by nearly 7- and 9-fold, respectively, while voriconazole (400 mg orally every 12 hours for 1 day, then 200 mg every 12 hours for 8 days) increased the same values by 7- and 11-fold, respectively. Another dual inhibitor, boceprevir (800 mg three times a day for 11 days), increased the Cmax and AUC of a single 2 mg dose of sirolimus by 10- and 17-fold, respectively. When sirolimus 2 mg once a day was coadministered with the moderate dual inhibitor erythromycin (ethylsuccinate salt 800 mg every 8 hours) in 24 study subjects, sirolimus Cmax and AUC increased by more than 4-fold each, while erythromycin Cmax and AUC also increased by more than 1.5-fold each.

MANAGEMENT: Concomitant use of sirolimus with potent CYP450 3A4 and/or P-gp inhibitors should generally be avoided. The manufacturers of posaconazole and voriconazole consider coadministration with sirolimus to be contraindicated. Some authorities recommend avoiding concomitant use of sirolimus during and for 2 weeks after treatment with itraconazole.